1. Field of the Invention
The present invention relates to a piston behavior. analyzing sensor mounting structure suitable for mounting on a cylinder block sensors for measuring a gap between a piston and an associated cylinder liner to analyze the behavior of a piston while the engine is running.
The present invention also relates to a piston behavior analyzing method for analyzing the behavior of a piston through variation in gap between the piston and an associated cylinder liner with reference to the crank angle.
2. Description of the Related Art
It is important to analyze various data while the engine is running in order to improve the quality of the engine. For instance, in a case where the cause of abnormal noise is considered to be the striking noise of a piston, the behaviors of pistons may be analyzed. In analyzing the behaviors of the pistons, since the pistons adapted to reciprocate within associated cylinder liners have required gaps relative to the inner circumferential surfaces of the cylinder liners, the pistons are free to move radially within the cylinder liners, whereby the movements thereof can be detected as variation in gap between the pistons and the associated cylinder liners, thereby making it possible to perform the aforesaid analysis of the piston behaviors from the result of the detection.
On the other hand, in order to detect the overheat of pistons while an engine is running, for example, Japanese Patent Unexamined Publication No. Hei. 4-140430 discloses a structure in which gap sensors are provided on a cylinder bock of the engine to detect gaps between the pistons and associated cylinder liners. The behaviors of the pistons can also be analyzed using gap values detected by the gap sensors so provided.
In the Japanese Patent Unexamined Publication No. Hei. 4-140430, the gap sensors are provided on a piston bottom dead center side of the cylinder liners, and the gap detection at the bottom dead centers of the pistons provide a problem that accurately grasping the behaviors of the pistons is insufficient.
To cope with this, it is necessary to detect gaps on a piston top dead center side of the liners where the behaviors of the pistons tend to be unstable. In a case where gap sensors are provided on the top dead center side, however, the sensors are largely affected by heat from combustion chambers, this causing various problems. For example, in a case where the sealing properties between the sensor mounting portion and the piston (oil rings) is deteriorated, lubricating oil starts to leak from there, causing a problem that the consumption of oil is increased. In addition, with the Japanese Patent Unexamined Publication No. Hei. 4-140430, there is another problem that gaps in axial directions of a crankshaft cannot be detected.
In addition, gap values detected by the gap sensors are largely affected by the mounting conditions of the gap sensors, causing a problem that the inaccurate mounting of gap sensors results in a deterioration in detection accuracy. In addition, while the engine is running, the effect of heat on the gap sensor mounting positions varies as the engine speed or load varies. In a case where a gap sensor accommodating case is made of stainless steel, while the cylinder block is made of aluminum, for example, there is caused a certain distortion between the accommodating case and the engine by virtue of the difference in the amount of deformation by the thermal expansion caused by heat, and this causes in turn a problem that the mounting positions of the gap sensors relative to the cylinder liners are shifted several xcexcm relative to those set when the gap sensors were mounted. In addition, when the engine speed is fast, there is a risk of a deterioration in gap detection accuracy being caused at the top dead center of the piston by virtue of the difference in response frequency between the gap sensors and crank angle sensors.
An object of the present invention is to solve the above problems inherent in the prior art.
In particular, an object of a first aspect of the invention is to realize a piston behavior analyzing sensor mounting structure for detecting the behaviors of pistons at top dead center positions thereof without any problem.
According to the first aspect of the invention, the object thereof is achieved by a piston behavior analyzing sensor mounting structure for mounting on a cylinder block (6) sensors (7a, 7b, 8a, 8b) for detecting gaps between pistons (4a, 4c) and associated cylinder liners (3a, 3c) on at least top dead center sides of the pistons (4a, 4c) for analysis of the behaviors of the pistons (7a, 7b, 8a, 8b) while an engine (1) is running, wherein accommodating cases (11) for the sensors (7a, 7b, 8a, 8b)are provided so as to pass through a water jacket (10) surrounding the cylinder liners (3a, 3c).
According to this structure, the accommodating cases can preferably be cooled by the cooling water and the sensors can in turn be cooled via the accommodating cases so cooled, whereby the effect of heat from the combustion chambers can be reduced.
In particular, the accommodating cases (11) are fixed on the cylinder liner sides, and portions of the accommodating cases (11) located more outwardly of the water jacket (10) may be sealed with a sealing member (16) in a state in which a thermal deformation of the accommodating cases (11) is possible relative to the cylinder block (6). According to this construction, even if the cylinder block is deformed by virtue of heat from the combustion chambers, the accommodating cases can securely be sealed.
In addition, portions of the sensors (7a, 7b, 8a, 8c) facing the interiors of the cylinder liners (3a, 3c) are constructed so as to be covered with lids (15) of a heat resistant resin. According to this construction, the sensors can be protected against heat from the combustion chambers. In addition, since the lids are made from the resin, not only is there no risk of the piston being damaged but also easy machining is possible, whereby cylinder bores can be machined after the lids are installed and good sealing properties can also be provided.
Furthermore, the sensors (7a, 7b) are constructed so as to be disposed in such a manner as to extend from a side of the cylinder block (6) in an axial direction of a crankshaft (5) toward the interior of the cylinder liner (3a). According to this construction, since it is possible to detect a relatively large deformation of a top land of the piston in the axial direction of the crankshaft, the accuracy with which the behavior of the piston is detected can be improved.
In addition, the sensors (7a, 7b) are constructed so as to be disposed in such a manner as to extend from a side of the cylinder block (6) which avoids a direction normal to the axis of the crankshaft (5) toward the interior of the cylinder liner (3a) and in an end face (6f) of the cylinder block (6) which is farthest away in an axial direction of the crankshaft (5) from a portion where a thrust control portion (17) for the crankshaft (5) is provided.
According to this construction, the position of the top land of the piston which is located at the position away from the thrust control portion and is liable to vary largely in a thrust direction can preferably be detected with high accuracy, and the mounting structure of the sensors is prevented from getting complicated, the cylinder block being thus prevented from getting large in size. In addition, the sensors only have to be disposed on the side which avoids the direction normal to the axis of the crankshaft, in other words, at an angle of substantially 180 degrees or less than 180 degrees relative to the crankshaft axis. This disposition of the sensors makes it possible to detect the behavior of the piston in the axial direction of the crankshaft.
Furthermore, the first sensors (7a, 7b) are disposed so as to extend from a side of the cylinder block (6) in an axial direction of a crankshaft (5) toward the interior of the cylinder liner (3a), and the second sensors (8a, 8b) are disposed so as to extend from a side of the cylinder block (6) which is normal to the axis of the crankshaft (5) toward the interior of the cylinder liner (3c). According to this construction, since the displacements of the pistons in the axial direction of the crankshaft and the direction normal to the axial direction of the crankshaft, respectively, can be detected, the behaviors of the pistons can be grasped with accuracy.
Moreover, there is provided a piston behavior analyzing sensor mounting structure for mounting on a cylinder block (6) sensors (7a, 7b) for detecting gaps between a piston (4a) and an associated cylinder liner (3a) on at least a top dead center side of the piston (4a) for analysis of the behavior of the piston (4a) while a multi-cylinder engine is running, wherein an introduction port (6w) is formed in the cylinder block (6) for introducing cooling water discharged from a water pump (18), and wherein the sensors (7a, 7b) are disposed so as to extend toward the interior of a cylinder liner (3a) which is closest to the cooling water introduction port (6w).
According to this construction, since the sensors are disposed at the position having the highest cooling efficiency, the effect of heat from the combustion chamber on the sensors can be reduced as much as possible.
In addition, an object of a second aspect of the invention is to prevent as much as possible the generation of detection errors that would be caused by various external factors in sensors for detecting a gap between a piston and an associated cylinder liner while an engine is running. According to the second aspect of the invention, the object is achieved by a piston behavior analyzing method for analyzing the behavior of a piston (4c) through change in gap between said piston (4c) and an associated cylinder liner (3c) in response to the angle of an associated crank while an engine is running, comprising the steps of detecting a gap between the piston (4c) and the associated cylinder liner (3c) with a sensor (8a) provided in the cylinder liner (3c), obtaining a variation (xcex94V) between a reference value corresponding to an abutment state between the piston (4c) and the cylinder liner (3c) and a minimum value (V min) in operation constituted by a minimum value among gap values (V) detected while the engine is running, and correcting the gap values (V) detected while the engine is running by an amount equal to the variation (xcex94V) for an actual gap value.
According to this construction, the gap sensors mounting portion is subjected to the effect of heat generated when the engine speed or load varies, and even if the mounting positions of the gap sensors in the cylinder liner are shifted relative to those set when they were mounted in the cylinder liner, an error can be eliminated from the gap values detected while the engine is running by performing a zero correction with the gap minimum value while the engine is running being regarded as a zero position where the piston comes into abutment with the cylinder liner.
In particular, the minimum value among the gap values (V) detected while the engine is running is taken over a plurality of numbers of cycles, and wherein the minimum value (V min) in operation is calculated based on a plurality of the minimum values so taken. According to this, since a plurality of minimum values are taken which constitute a reference in performing the zero correction, the minimum value in operation can be calculated with high accuracy for performing the zero correction by calculating an average value from those minimum values so taken.
In addition, there is provided a piston behavior analyzing method for analyzing the behavior of a piston through change in gap between the piston and an associated cylinder (3c) liner in response to the angle of an associated crank while an engine is running, comprising the steps of detecting positions (E, F) before and after a top dead center of the piston (4c) where piston rings of the piston pass with the sensor (8a) provided in the cylinder liner (3c) for detection of the gap, and making an intermediate point between two points of the positions (E, F) where the piston rings pass the position of a top dead center when analyzing the behavior of the piston.
According to this construction, since the piston position is directly seen with the sensor for detecting the gap between the piston and its associated cylinder liner, the top dead center can be detected with accuracy by detecting the piston positions before and after the top dead center thereof, and therefore, even if there is generated a difference in response frequency when the engine speed is fast between a crank angle detected by the crank angle sensor separately provided and the top dead center so detected, a correction can be performed therefor.